Shinichiro Hasegawa, 82, who runs a small farm to supplement his pension, found £270 worth of chestnuts had disappeared from his farm in Ibaraki, north of Tokyo.

Many farmers still think of the countryside as largely crime-free and, like Mr Hasegawa, have no theft insurance and never lock their storehouses.

"These thefts would have been unthinkable before," said Mr Hasegawa.

"I assume it is because of the recession. People's lives are getting harder and unemployment is rising. But I never imagined anyone would steal my chestnuts."

There were 480 farm thefts up to the end of August, nearly half as much again as last year. But the financial loss has leapt more than 80 per cent, reflecting the professionalism of thieves going for intensively farmed foods that fetch high prices.

In Mr Hasegawa's case, the thieves knew they should strike soon after heavy rain, when chestnuts fall and must be collected. They also took only the chestnuts that Mr Hasegawa had polished, leaving those that were not ready for sale.

In other cases, the thieves have known how to pick the most popular strains of rice and best fruit from fully stocked storehouses.

In Aichi, central Japan, thieves made off with thousands of musk melons which sell for up to £55 each. In Yamagata, renowned Sato Nishiki cherries that can sell for £100 a pound have disappeared from orchards.

A cold, wet summer has meant a bad crop. This has already hit farmers hard, but the rise in food prices has made their crops a juicier target for criminals.

Masahiko Obayashi, 56, a grape farmer, has organised crime patrols in his village in Gunma, north of Tokyo.